filler metal
noun
metal supplied in the form of a welding rod, sometimes flux coated, melted by an arc or a flame into a joint between components to be joined
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012